An ideal optical path, such as a system of lenses for a microscope, would provide undistorted magnification of features in the object with uniform resolution over an entire field of view. However, practical lenses, mirrors, and camera systems introduce aberrations that cause the image resolution to vary over the image plane. One such well known aberration is astigmatism. Astigmatism is defined as the presence of separate focal lengths, along the principal axis, for rays of light traveling in different rotational planes through the optics system. Optical paths of all types suffer from astigmatism.
A method is needed to measure the severity of this aberration so that optical paths that are excessively degraded by astigmatism can be repaired or adjusted. Therefore, the invention provides an automated system that measures astigmatism in an optical path and provides an optical quality signal to alert other system components that the optical path is so effected.